Puerto Rico lies at the
eastern end of the major island chain of the Caribbean, the
Greater Antilles. The other islands in the chain, Cuba, Jamaica,
and Hispaniola (Haiti and the Dominican Republic) are larger
and geographically more diverse. Puerto Rico's total area, including
the neighboring islands it administers, is about 3,515 square
miles (9,104 square kilometers). The two largest island dependencies,
Vieques and Culebra lie east of Puerto Rico proper. In the west
are three smaller island dependencies; Mona, Monito, and Desecheo.
The relatively smooth coastline is fringed by many small islands
and cays, especially in the south and east. The island is roughly
rectangular in shape and stretches for 110 miles (180 kilometers)
from east to west between Punta Jiguero and Punta Puerca, with
a width from north to south averaging 35 miles (56 kilometers).
Deep oceanic waters fringe Puerto Rico. The Mona Passage, which
separates the island from Hispaniola to the west, is about 75
miles (120 kilometers) wide and more than 3,300 feet (1,000
meters) deep. Off the northern coast is the 28,000 foot (8,500
meter) deep Puerto Rico Trench, and to the south the sea bottom
descends to the 16,400 foot (5,000 meter) deep Venezuelan Basin
of the Caribbean. Only to the east is there a broad continental
shelf where the islands of Vieques and Culebra are structural
continuations of the nearby Virgin Islands.
Puerto Rico is topographically rugged; its surface consists
largely of hills, slopes, and mountains. The mountainous core
is formed by the Cordillera Central and the Sierra de Luquillo,
continuations of the Cordillera Central on neighboring Hispaniola.
Both mountain ranges represent uplifted old surfaces strongly
dissected by river erosion. Hill regions of equal irregularity
and unevenness extend north and south of these mountains. Only
30 percent of the island can be classified as level or undulating,
mostly in the form of an encircling narrow coastal plain.
The topographical structure affects Puerto Rico's climate and
soils. The soil lacks depth and plant nutrients, with less than
a third that of the coastal plain having average to good qualities
for agriculture. Overuse of low-quality and inadequate soil,
especially in the hilly regions and mountainous interior, has
contributed to damaging erosion of hillsides and gullies. Intensive
conservation practices are encouraged in order to limit land
use to pasture or forest development and to conserve water resources.
The island is situated firmly within the zone of the trade winds,
which blow from the east and northeast most of the year, and
it has equitable temperature ranges differentiated only by altitude:
tierra caliente (hot, tropical) on the plains and low hills
and tierra templada (moderate, subtropical) in the mountains.
Extreme temperatures are rare, the average minimum and maximum
being 63° F (17° C) in February and 88° F (31°
C) in August. Great variability in precipitation, however, is
the norm. Easterly waves, las ondas alisias, move westward within
the trade-wind zone and cause frequent intense rains that at
times last two to three days without interruption. Hurricanes
every so often strike Puerto Rico and every year some pass near
enough to affect the island's climate particularly causing heavy
precipitation during early fall, August to October. Cold fronts
during the winter months occasionally bring relatively cold
north winds, the "nortes", which drop the island's
north coast temperatures to about 60° F (16° C).
North of the mountainous
interior it is wet with between 80 and 120 inches (200 and 300
centimeters) of rain annually. At the northeastern end of the
island lies the El Yunque (The anvil) rain forest where the
sounds of the coqui frog can be heard in all its splendor at
night. In the south of the mountain backbone it is relatively
dry with between 40 and 50 inches (100 and 125 centimeters).
The high temperatures throughout the year result in high evaporation
rates of surface moisture so that a section of Puerto Rico has
semiarid conditions.
The natural vegetation of the island before it became inhabited
was forest. It ranged from low scrubby woodland, cactus scrub,
and mangrove in tidal lagoons along windswept coasts to luxuriant
tropical evergreen forests of the cordillera and sierras. Most
has disappeared, as virtually all of the island's lands have
been cultivated innumerable times. Only in those areas not amenable
to agricultural exploitation of any kind was natural vegetation
allowed to stand. Sites like the forest reserves of the Sierra
de Luquillo in the northeast and some swamps on private lands
are the sole remains of the once dense forest cover. Evergreen
tropical rain forest and mountain forest at higher altitudes
still survive at Luquillo. Tropical palm trees and tree ferns
still grow densely right up to the mountain crests. Elsewhere
semievergreen seasonal forests are found in the southern hills,
and dry woodland scrub and cactus savannas remain in coastal
areas of the south.
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